Method of sizing fibrous material



the like, will following description of a process of making- Patented Novo 1, 1 932 UNITED STATES PATENT- oarlcn I FRANCIS J. CURTIS, OI BELMONT, MASSACHUSETTS, ASSIGNOB IQ HERBIMAC CfiEHICAIi comramr, me, or no's'ron, MASSACHUSETTS, A eoaron'nrronor massacnnsn'r'rs METHOD 0] SIZING FIBROUS MATERIAL No Drawing.

My invention relates to sizing fibrousmaterial, particularly, but not exclusively, cellulose fibers, and is particularly useful in the production of paper products. r

The invention, which has among] its ob-. jects increasin the durability of. paper or e best understood from the paper constituting one embodiment of the invention, while the scope 'of the invention will be more particularly pointed out in the appended claims.

Heretofore, paper commonly has been made by beating cellulose fibers ina beater to which is added rosin size, the latter commonly made by boiling soda ash and rosin and atomizing the solution in water.

After the mixture has been beaten for a;

scribed prior process lacks durability in the sense that it is subject to chemical deterioraa tion. This deterioration is believed to be largely due to the acidity of the paper pulp consequent upon the addition of the necessary amount of alum to secure efiective'sizing. It has been found that the mixture of cellulose' fibers and rosin size is very alkaline,

commonly having a hydrogen ion concentra'- tion equivalent to a H value of 9 or 10, or even more. The a dition of the requisite amount of alum to secure pro er sizing, it has been found commonly re uces the pH value to somewhere around 4.5 to 4.8, which indicates considerable acidity. It is believ ed that the phenomenon, which occurs in this prior process, is that the alum in solution disassociates into sulphuric acid and colloidal alumina, the sulphuric acid acting to Application filed August 10, 1929. Serial No. 885,084.

precipitate the rosin from the size, and the colloidal alumina forming a so-calld colloidal complex between the alumina, cellulose, and rosin, it being understOodthat colloids havin the same electrical charge will not unite in the absence of a bond hav ing an opposite electrical charge, and that the cellulose and rosin "colloids both have a negative electrical charge which will pre vent their cementing in the absence of the colloidal alumina which has a positive electrical charge. It has been found that it the sized pulphas an acidity indicated by a pH value which is not lower than about 6 the paper produced is not subject to" chemical deterioration, but that in most instances, if only suflicient alum is added to secure this pH value, improper sizing will result, the

sizing in such cases being due merel to a mechanical mixture of the precipitate rosin and cellulose fibers. Therefore, it is nee;- essary, in the prior process, to use suflicient alum to supply the necessary amount of col loidal alumina to secure effective sizing,

with the result that the pH value of the pulp is reduced to a value'at which chemical deterioration of the sized paper occurs.

.According to the improved process, the

requisite amount of collidal alumina is provided in substantially alkaline combination,

as distinguished from acid combination. It has been found that the pH value of the pulp may be controlled within any desired limits, while securing suflicient alumina to effect proper sizing, by reducing the amount of alum added to the pulp according to the prior process, and using sodium aluminate or increasing the amount of alumina above that provided b enough alum is a ded to give the'necessar acidity to precipitate the rosin from the a the alum. Preferably,

kaline IOSln size, the remaining necessary alumina being provided by the sodium ala minate. With the improved process, by v'arying the proportionsmf alum and sodium'alu minate, any desired pH valueof the pulp and amount of alumina therein may be secured, whereas with the prior process, increasing the amount of alumina necessarily increases the amount 'of acid present, with the result for that when proper sizing is effected by the prior process, thepH value is so low that the paper produced-and the machiner employed for producing it, particularly t e ex-' pensive wire belts, are subject to chemical eterioration, which m aterially reduces the life of both the paper and said machinery.

The relative amounts of alum and sodium aluminate can be varied within wide limits, depending upon the condition of the paper ulp and the kind and grade of paper produced. When making paper, the alum and sodium aluminate prefera ly are added in aqueous solution, and referablyat the same continually testing samplesof the liquor for time, but to prevent ocking, the, two solutions are not mixed before adding them to the pulp.

As one example of the practice of the method, but without limitation thereto, I have found that satisfactory results can be obtained, when using standard sulpbite pulp beaten with 2% by weight of rosin, the latter in the form of the above described rosin size, by adding alum 4 and sodium aluminate (NA O.Al O in the ratio of 3: 1, with the total alumina (A1 0 the equivalent of 3% of alum based on the Wei ht of pulp. With this mixture sizing is o tained, at a pH value of 6.5, as satisfactor as that obtained byuse of alum alone at a pll .value. of 4. In practice, the character of the pulp and amount of rosin employed varywidel according to the kind and grade of paper to e made. In practising the invention the necessary amounts of alum and sodium aluminate may be determined for given conditions by gradually adding alum to the first beater handling the material, and

H value until a pH value is obtained which .mdicates the rosin is precipitated. Commonly for usualrosin size this pH value will be about 5, but. for any rosin size the value can be readily determined by previous sample tests.- After precipitation of the rosin, sodium aluminate maybe gradually added to the beater until tests of samples of liquor drawn from the beater indicate the desired pH value of the pulp. Preferably a final pH value of about 6.5 is secured, but good results will be obtained with pH values between 5 and 7. It will be understood that the pH value of the samples of liquor may bequickly obtained by use oi any of the several 'lmown electrometrie or colorimetric methods.

As substitutes for the specific rosin hereinbefore mentioned other forms of colloidal rosin, starch glue, and other negatively charged colloids, may be employed, and the invention is applicable to soda and other tating the rosin and pulps commonly employed in the art as well i as to sulphite pulp.

It will be understood that wide deviations may be made from the examples of the invention herein described without departing from its spirit.

1. The process of cementing negatively charged colloidal size to the cellulose fibers in a mixture of the two which comprises adding alum and sodium aluminate.

2. The process of sizing cellulose and like fibers which comprises mixing said fibers with rosin size, precipitating the rosin by adding alum tothe mixture, and controlling the pH value of the mixture by adding sodium aluminate thereto.

3., The process of sizing cellulose and like fibers which comprises mixing said fibers with rosin size, precipitating the rosin by adding alumv to the mixture, and augmenting the amount of alumina provided by the alum and controlling the pH value of the mixtime by adding sodium aluminate.

4. The process of producing sized paper products which comprises beating cellulose fibers with rosin size, precipitating the rosin in the beaten mixture by adding alum, and controlling the pHivalue of the mixture by adding sodium aluminate thereto.

5. The process of producing sized paper products which comprises beating cellulose fibers with rosin size, precipitating the rosin by adding alum to the beaten mixture, and augmenting the amount of alumina provided by the alum and controlling the pH value of the mixture by adding sodium aluminate.

6. The process of producing sized paper- .products which comprises beating cellulose 

